1. Field of the Invention
This invention relates to a nozzle head for ink jet system, and more particularly to an ink jet nozzle head provided with a plurality of nozzle slit openings.
2. Description of the Prior Art
In conventional printers and information output terminals, various kinds of output information are recorded on the recording paper by causing wire heads, printing types or the like to impinge upon the recording paper through an ink ribbon intervening therebetween. With the conventional systems, however, noise of a considerably high level occurs at the time of recording, affecting the working environment in relatively quiet offices. To solve this problem, use is made of the so-called ink jet system for output apparatuses in which a liquid ink is jetted onto the recording paper to record output information thereon. The ink jet systems are divided into the charging control system, ink-on-demand system, electric field control system and ink mist system. In the charging control system, an ink is dispersed into droplets by a vibrator, electrostatically charged, and then deflected by the application of an electric field to record the output information. In the ink-on-demand system, a pressure is applied to an ink reservoir by a piezoelectric element according to the output information to make the ink jet onto the recording paper. In the electric field control system, a potential is applied between nozzle openings and the recording paper according to the output information, and an ink is withdrawn from the nozzle openings by the electrostatic attraction force to record the information on the recording paper. In the ink mist system, an ink stored in an ink reservoir is converted into mist by a vibrator, the ink mist thus formed is selectively ionized by electric discharge according to the output information, and the ionized ink is directed onto the recording paper by the electrostatic attraction force. The nozzle head in accordance with the present invention is in the category of the electric field control system.
The conventional nozzle head of the electric field control system has a single nozzle opening, and the nozzle head linearly scans the recording paper to record the information thereon. With this conventional method, however, the recording speed is relatively low because the nozzle head is mechanically driven. To solve this problem, it has been proposed to use a nozzle head provided with a plurality of nozzle openings arranged in the direction of the scanning line. In this method, instead of mechanically driving the nozzle head, a potential is selectively applied to respective nozzle openings according to the output information, and the information corresponding to one line is recorded nearly simultaneously.
FIG. 1 is a schematic view showing an ink jet recording apparatus provided with a conventional ink jet nozzle head having a plurality of nozzle openings. In FIG. 1, recording paper 3 is positioned between a nozzle head 2 having many nozzle openings and needle-like electrodes 5 corresponding to the respective nozzle openings. A liquid ink is pressurized by a pressure pump 1 or static pressure of the ink to form hemispheric menisci at the nozzle openings. When a voltage is applied between a voltage applying terminal 4 and the respective needle-like electrodes 5 according to the output information, namely when a voltage is selectively applied to the respective needle-like electrodes 5 according to the output information, the ink minisci formed at the corresponding nozzle openings are selectively caused to jet onto the recording paper 3 to record the information. The recording paper 3 is moved by feed rollers 6, and the output information of the next line is recorded. In this way, the output information is recorded on the whole recording paper 3.
With the nozzle head having many nozzle openings, it is possible to record the information of one line nearly simultaneously without mechanically driving the nozzle head to linearly scan the recording paper. Therefore, the output information can be recorded at a high speed. In the past, the nozzle head having a plurality of nozzle openings was manufactured by forming the nozzle grooves by means of machining. However, when the output information is image information which should be recorded at a high density and a high resolution, it is necessary to form nozzles having very small openings at narrow intervals in order to obtain an image output of high quality. With the machining processes, however, the dimensional accuracy is limited and it is difficult to form nozzles capable of providing a high recording density and a high resolution.